Change slug and date placeholders to values

Closes #4121
Custom permalink UI

References #3920
Merge pull request #4323 from jaswilli/issue-4121

Change slug and date placeholders to values
Merge pull request #4217 from PaulAdamDavis/permalinks-ui

[WIP] Custom Permalink UI
Escapes strings

closes #4328

- Escapes metaTitle, metaDescription, blog url, blog title, tags
- Updates tests
- Adds test for metaTitle and metaDescription with double quotes